The folding of flat sheets of a material to produce a container, such as a box, jacket or the like, has long been known in the prior art. In order to form the container by folding the flat sheet, in most cases the fold has been accomplished by tangential bending. Tangential bending occurs when a free portion of the flat sheet to be bent is progressively wrapped around the edge of a shim. In this manner, the portion of the flat sheet extending beyond the shim is approximately tangent to the edge as the fold is made.
While tangential bending has proven satisfactory in producing a wide variety of different containers, tangential bending and other prior art types of bending have not proven satisfactory for certain uses. In particular, where tangential bending is used to produce a flat jacket to contain a magnetic disk, particularly a floppy disk, the interior of the jacket tends to press down and damage the magnetic disk. This problem is due to the fact that tangential bending produces essentially a two-dimensional, wedge-shaped fold. The magnetic disk then becomes pressed between the two surfaces in the wedge.